The technology progress of cathode materials for lithium batteries, such as LiCoO₂, LiNi_xCo_yMn_zO₂, LiMn₂O₄ and LiFePO₄, is reviewed. The advantages and disadvantages, market status of different cathode materials are introduced. The common problems including poor product quality and shortage of R&D inputs in the current cathode materials industry are analyzed. Increasing R&D investment, enchancing industry-academic collaboration and application of advanced equipment are suggested as solution proposal. The future prospect of the cathode materials industry is predicted according to our knowledge.

Energy storage technologies show broad application prospects in renewable energy systems such as wind and solar energy, and in the construction of smart grid/micro grids. Lead-acid batteries have dominated the market in stationary energy storage due to their advantages of low price, high-unit voltage, stable performance, and a wide operating temperature range. However, lead-acid batteries under hybrid electric veheciles (HEV) and renewable-energy applications must be operated at different state-of-charge windows. In particular, under high-rate partial-state-of-charge (HRPSoC) duty, lead-acid batteries fail prematurely due to the sulfation of the negative plates. Lead carbon ultrabatteies are a new hybrid energy storage device, which combines a lead acid battery and an asymmetric supercapacitor in single unit, with the advantage of both high energy of lead acid battery and high power of supercapacitor. The uneven distribution of lead sulfate across the cross-section of negative plate during discharge and the early evolution of hydrogen during charge should be suppressed. There fore, lead carbon ultrabatteies have longer cycling life in a wider state-of-charge window, which is suitable for high rate cycling and pulse applications. The concept and the basic principles of lead carbon ultrabatteries and its recent developments are summarized.

Lithium-selenium batteries have attracted significant attentions owing to its high specific volumetric capacity (3254 mA·h·cm^-3). In this review, we focus on the latest progress in the selenium/carbon cathode materials for lithium-selenium batteries. After discussing the major problems and challenges on the lithium-selenium batteries, we attempt to put forward the possible strategies. At last, the research directions of lithium-selenium batteries in the future are forecasted.

Thermochemical energy storage has a potential for a wide range of heat storage applications. Such a method could offer an efficient energy conversion, long-term storage and long-distance transport of energy. This paper reviews the state of the art development in the area particularly for medium to high temperature (573~1273 K) applications including metallic hydrides, the redox system, organic systems, hydroxide systems and ammonia systems. We summarize numerical and experimental work as well as technological development in the area and present the key.

Underwater compressed air energy storage (UCAES) uses the hydrostatic pressure of water to realize isobaric storage of the compressed air. The advantages of such a method include high efficiency, reduced topographical limitations, and flexibility in storage scale, providing a potentially suitable technology for storing offshore renewable energy. In this paper, a brief review is given first on emerging compressed air energy storage technologies, the focus is the on the UCAES. We introduce the working principle and current state of research in the UCAES. We also perform an analyses on the technology particularly UCAES combined with the use of a flexible energy bag. Finally, key future technology developments and outlook of the UCAES are summarized.

According to the progress of studies on the thermal characteristic of lithium-ion battery, the heat generation mechanism and thermal models of lithium-ion battery have been summarized, especially the electrochemical thermal coupling model, electro-thermal coupling model and thermal abuse model. In addition, the future work on thermal effects and the establishment of thermal model of lithium-ion battery were prospected.

The safety and thermal runaway processes of a lithium ion battery and its toxic leakage effects on human and environments are elaborated and discussed in detail. The EV power lithium ion battery was used as example to analysis its impact to a city environment. One of the representative combustion toxics CO was analyst in quantity from three different 10 A·h lithium ion cell (LiFePO₄, LiMnO₂ and NMC) combustion experiment. It shows that the toxics safety problems of lithium ion battery can not be ignored any more.

A KF-KCl based composite phase change material has been successfully fabricated using power sintering method with SiO₂ as matrix, vinyl alcohol as binder and B₂O₃ as sintering additive. The formulation and the optimal sintering temperature are obtained through experiments. XRD analyses indicate a good chemical compatibility of the system. TG-DSC analyses show an endothermic peak at 591.7 ℃ with a latent heat of 157.4 J^-1·g. The results demonstrate that the composite PCM has a high energy density with potential for high temperature thermal storage without using a container.

Distributed combined cooling heating and power (CCHP) systems can be regarded as an extension of traditional distributed energy supply system. A CCHP system not only inherits the advantages of the traditional system, but also bring other benefits such as overall energy efficiency and system economy. We consider the use of an energy storage unit in the CCHP system to ensure the system to maintain the energy output and the load demand match, on top of the ability of supplying cold, heat, and electricity load, while maintaining high efficiency. In this paper, the role of the energy storage unit in distributed CCHP systems are discussed and quantified using simulation tools. The results confirmed that the use of an energy storage unit helps enhance the system stability and efficiency.

This paper briefly reviews the recent developments in heat storage media and materials for containerizing the medium. Analyses are carried on high temperature heat storage devices using electricity to produce heat, aluminum-silicon alloys as the storage medium and S316 as the container material. The results suggest the feasibility of the products both technically and economically.

Using renewable energy is one of the effective methods to reduce building energy consumption. In this paper, a solar hot air heating system is combined with phase change material wall with an aim to improve the efficiency of solar heating. With such a heating system, the instability due to intermittency of solar energy and the efficiency of solar energy utilisation could be improved. Experimental testing and numerical modelling in the ANSYS environment have been carried out on the integrated heating system. The characteristics of phase change material wall and the percentage of the phase change materials in the wall are determined and the contribution of the phase change material is obtained. The results indicate that, compared with the non-heating case, the combined heating system increases the indoor temperature by 7 ℃ to 15 ℃ on average. When the air inlet temperature of the collector is between 37 ℃ and 77 ℃, the phase change material is fully utilised with approximately 40% of the wall performing phase change function. Analysis of the results suggests the combined heating system be better than solar air heating only system.

Paraffin wax based phase change material (PCM) has a low thermal conductivity, which may significantly affect the heat transfer and solidification rates. Simulations are carried out to investigate the solidification behavior of a paraffin based thermal storage device containing graphite foam. The results show a more even temperature distribution and a significantly reduced solidification time due to the use of the high thermal conductivity graphite foam. Analyses are performed on the influence of fluid operating conditions including inlet temperature and velocity, on the solidification process of the paraffin/graphite foam. The results demonstrate that the solidification time decreases with increasing the inlet velocity and/or reducing the temperature of cooling water. Moreover, it is found that natural convection of the PCM can accelerate the solidification rate of the PCM.

Compressed air energy storage (CAES) technology is one of the large-scale energy storage technologies with great commercial potential. This paper reports a simulation study on the CAES using the Aspen Plus software package. Exergy analyses are carried on the performance of the CAES and the result indicates the largest exergy loss in the combustion chamber. A sensitivity analysis is performed on the effects of the component efficiencies on the exergy loss of the CAES system. The results show that the efficiency of the combustion chamber has the biggest influence on the system exergy efficiency, while the adiabatic efficiency of expansion turbine has the smallest influence.