The increasing interest in energy storage for the grid can be attributed to multiple factors, including the capital costs of managing peak demands, the investments needed for grid reliability, and the integration of renewable energy sources. Although existing energy storage is dominated by pumped hydroelectric, there is the recognition that battery systems can offer a number of high-value opportunities, provided that lower costs can be obtained. The battery systems reviewed here include sodium-sulfur batteries that are commercially available for grid applications, redox-flow batteries that offer low cost, and lithium-ion batteries whose development for commercial electronics and electric vehicles is being applied to grid storage.

Electrical Energy Storage for the Grid: A Battery of Choices

In the previous paper Ralph Brodd and Martin Winter described the different kinds of batteries and fuel cells. In this paper I will describe lithium batteries in more detail, building an overall foundation for the papers that follow which describe specific components in some depth and usually with an emphasis on the materials behavior. The lithium battery industry is undergoing rapid expansion, now representing the largest segment of the portable battery industry and dominating the computer, cell phone, and camera power source industry. However, the present secondary batteries use expensive components, which are not in sufficient supply to allow the industry to grow at the same rate in the next decade. Moreover, the safety of the system is questionable for the large-scale batteries needed for hybrid electric vehicles (HEV). Another battery need is for a high-power system that can be used for power tools, where only the environmentally hazardous Ni/ Cd battery presently meets the requirements. A battery is a transducer that converts chemical energy into electrical energy and vice versa. It contains an anode, a cathode, and an electrolyte. The anode, in the case of a lithium battery, is the source of lithium ions. The cathode is the sink for the lithium ions and is chosen to optimize a number of parameters, discussed below. The electrolyte provides for the separation of ionic transport and electronic transport, and in a perfect battery the lithium ion transport number will be unity in the electrolyte. The cell potential is determined by the difference between the chemical potential of the lithium in the anode and cathode, ∆G ) -EF. As noted above, the lithium ions flow through the electrolyte whereas the electrons generated from the reaction, Li ) Li+ + e-, go through the external circuit to do work. Thus, the electrode system must allow for the flow of both lithium ions and electrons. That is, it must be both a good ionic conductor and an electronic conductor. As discussed below, many electrochemically active materials are not good electronic conductors, so it is necessary to add an electronically conductive material such as carbon * To whom correspondence should be addressed. Phone and fax: (607) 777-4623. E-mail: stanwhit@binghamton.edu. 4271 Chem. Rev. 2004, 104, 4271−4301

http://www.chemie.uni-regensburg.de/Anorganische_Chemie/Vortrag/StudentenWS06-07/Vortrag_Amereller.pdf

Lithium Batteries and Cathode Materials

Li-ion battery materials: present and future

The is a comprehensive review on the needs and potential storage technologies for electrical grid that is expected to integrate significant levels of renewables. This review offers details of the technologies, in terms of needs, status, challenges and future R&d directions.

/pdf/electrochemical-energy-storage-for-green-grid-22ttg0wpz1.pdf

Electrochemical Energy Storage for Green Grid

Energy production and storage have become key issues concerning our welfare in daily life. Present challenges for batteries are twofold. In the first place, the increasing demand for powering systems of portable electronic devices and zero-emission vehicles stimulates research towards high energy and high voltage systems. In the second place, low cost batteries are required in order to advance towards smart electric grids that integrate discontinuous energy flow from renewable sources, optimizing the performance of clean energy sources. Na-ion batteries can be the key for the second point, because of the huge availability of sodium, its low price and the similarity of both Li and Na insertion chemistries. In spite of the lower energy density and voltage of Na-ion based technologies, they can be focused on applications where the weight and footprint requirement is less drastic, such as electrical grid storage. Much work has to be done in the field of Na-ion in order to catch up with Li-ion technology. Cathodic and anodic materials must be optimized, and new electrolytes will be the key point for Na-ion success. This review will gather the up-to-date knowledge about Na-ion battery materials, with the aim of providing a wide view of the systems that have already been explored and a starting point for the new research on this battery technology.

Na-ion batteries, recent advances and present challenges to become low cost energy storage systems

LiFePO 4 powders were synthesized under various conditions and the performance of the cathodes was evaluated using coin cells, The samples were characterized by X-ray diffraction, scanning electron microscope observations, Brunauer, Emmett, and Teller surface area measurements, particle-size distribution measurements, and Mossbauer spectroscopy. Ab initio calculation was used to confirm the experimental redox potentials and Mossbauer parameters. The choice of a moderate sintering temperature (500°C 95% of the 170 mAh/g theoretical capacity at room temperature. There are two main obstacles to achieving optimum charge/discharge performance of LiFePO 4 : (i) undesirable particle growth at T > 600°C and (ii) the presence of a noncrystalline residual Fe 3+ phase at T < 500°C.

https://iopscience.iop.org/article/10.1149/1.1348257/pdf

Optimized LiFePO4 for Lithium Battery Cathodes

A potential 4 V cathode material for lithium batteries was investigated. The crystal chemistry of the olivine-type of Li(Mn y 2+ Fe 1-y 2+ )PO 4 (discharged state) and its delithiated form (Mn y 3+ Fe 1-y 3+ )PO 4 (charged state) were comparatively studied using X-ray diffraction, Mossbauer spectroscopy, and ab initio calculations. A strong oxidizer, nitronium tetrafluoroborate, NO 2 BF 4 , was used for chemical delithiation of Li(Mn y 2+ Fe 1-y 2+ )PO 4 to obtain (Mn y 3+ Fe 1-y 3+ )PO 4 . The strong electron/lattice interaction induced by the trivalent manganese (3d 4 ) in (Mn y 3+ Fe 1-y 3+ )PO 4 (charged state) is highlighted as the intrinsic obstacle to generating the full theoretical capacity (ca. 170 mAh/g) of the Mn-rich phase (y >0.8), followed by an efficient cathode performance of the optimized Li(Mn 0.6 Fe 0.4 )PO 4 .

Crystal Chemistry of the Olivine-Type Li ( Mn y Fe1 − y ) PO 4 and ( Mn y Fe1 − y ) PO 4 as Possible 4 V Cathode Materials for Lithium Batteries

Olivine-type cathodes: Achievements and problems

Vying for newer sodium-ion chemistry for rechargeable batteries, Na2FeP2O7 pyrophosphate has been recently unveiled as a 3 V high-rate cathode. In addition to its low cost and promising electrochemical performance, here we demonstrate Na2FeP2O7 as a safe cathode with high thermal stability. Chemical/electrochemical desodiation of this insertion compound has led to the discovery of a new polymorph of NaFeP2O7. High-temperature analyses of the desodiated state NaFeP2O7 show an irreversible phase transition from triclinic (P1) to the ground state monoclinic (P21/c) polymorph above 560 °C. It demonstrates high thermal stability, with no thermal decomposition and/or oxygen evolution until 600 °C, the upper limit of the present investigation. This high operational stability is rooted in the stable pyrophosphate (P2O7)4– anion, which offers better safety than other phosphate-based cathodes. It establishes Na2FeP2O7 as a safe cathode candidate for large-scale economic sodium-ion battery applications.

Sai-Cheong Chung

Papers

Optimized LiFePO4 for Lithium Battery Cathodes

Crystal Chemistry of the Olivine-Type Li ( Mn y Fe1 − y ) PO 4 and ( Mn y Fe1 − y ) PO 4 as Possible 4 V Cathode Materials for Lithium Batteries

Olivine-type cathodes: Achievements and problems

Na2FeP2O7: A Safe Cathode for Rechargeable Sodium-ion Batteries

Reversible hydrogen decomposition of KAlH4