
The Gregorian calendar, like the , is a with 12 months of 28–31 days each. The year in both calendars consists of 365 days, with a being added to February in the . The months and length of months in the Gregorian calendar are the same as for the Julian calendar. The only difference is that the Gregorian calendar omits a leap day in three centurial years every 400 years and leaves the leap day unchanged. [pdf]
The Gregorian calendar, used in Europe and in a very large part of the world, takes its name from Pope Gregory XIII who set it up in 1582. This calendar is a correction to the previous calendar, the Julian calendar introduced by Julius Caesar in 46 BC. The starting point of Year 1 is an approximate date of the birth of Jesus.
By any criterion, the Gregorian calendar is substantially more accurate than the 1 day in 128 years error of the Julian calendar (average year 365.25 days).
It proposes two major corrections. The first is an 11-day jump in the calendar: the day after 4 October 1582 will be 15 October 1582, and 10 days are therefore removed from the calendar. The second is a new way of calculating leap years. In the Gregorian calendar, the tropical year was approximated to 365.2425 days.
The Gregorian calendar reduces the number of intercalary days to 97 in 400 years, as opposed to 100 intercalary days in 400 Julian years. The change is small but profound. It brings the mean length of the calendar year into much closer agreement with the tropical year, providing, a mean cal endar year of 365.2425 days.
There were two reasons to establish the Gregorian calendar. First, the Julian calendar assumed incorrectly that the average solar year is exactly 365.25 days long, an overestimate of a little under one day per century, and thus has a leap year every four years without exception.
The Gregorian calendar improves the approximation made by the Julian calendar by skipping three Julian leap days in every 400 years, giving an average year of 365.2425 mean solar days long. [ 82 ] This approximation has an error of about one day per 3,030 years [ s ] with respect to the current value of the mean tropical year.

Nowadays, materials with a core-shell structure have been widely explored for applications in advanced batteries owing to their superb properties. Core-shell structures based on the electrode type, including anod. . ••Core-shell structures show a great potential in advanced batteries.••. . Dramatic climate change and the limited availability of fossil fuels have spurred international interest in developing renewable energy technologies [1]. Efficient and environment. . In traditional LIBs, graphite with a relatively modest theoretical capacity of 372 mA h g−1 has often been chosen as the anode [31], [32]. Recently, novel core-shell structures for LI. . Apart from LIBs, core-shell structures are also employed in LSBs to improve their electrochemical performances. LSBs are promising electrochemical devices for future energy sto. . In recent years, SIBs have received increasing attention as alternative for LIBs in large-scale electric energy storage applications [284], [285]. SIBs have many advantages suc. [pdf]
Battery systems with core–shell structures have attracted great interest due to their unique structure. Core-shell structures allow optimization of battery performance by adjusting the composition and ratio of the core and shell to enhance stability, energy density and energy storage capacity.
Utilizing the features of the core–shell structure can improve battery performance. Core-shell structures show promising applications in energy storage and other fields. In the context of the current energy crisis, it is crucial to develop efficient energy storage devices.
Core-shell structures show promising applications in energy storage and other fields. In the context of the current energy crisis, it is crucial to develop efficient energy storage devices. Battery systems with core–shell structures have attracted great interest due to their unique structure.
High-entropy battery materials (HEBMs) have emerged as a promising frontier in energy storage and conversion, garnering significant global research interest. These materials are characterized by their unique structural properties, compositional complexity, entropy-driven stabilization, superionic conductivity, and low activation energy.
Core-shell structured materials manifest the potential to be optimized by adjusting their composition and the ratio of their core–shell configuration, therefore, they have been investigated comprehensively in the field of energy storage research.
Additionally, this method enables control over the distribution and size of sulfur within the core–shell structure, thereby optimizing energy storage performance. The internal cavity of the core–shell architecture reduces material volume expansion during lithiation, thereby improving cycling stability.

In large battery assemblies, which are integrated, for example, in electric vehicles or stationary storage systems, up to several thousand single battery cells are connected together. Every single cell connection influe. . Large battery assemblies are of particular interest both for the progressing electrification of mobility. . As mentioned in Section 1, the electrical contact resistances of cell connections are of high relevance for the quality of a battery assembly. To obtain transferable results, the electrical con. . The main characteristic of resistance spot welding is that only a small volume of the work pieces is melted and fused together. The welding heat is generated by the electrical power. . Ultrasonic welding is a solid-state welding technique. The work pieces are not melted but pressed and scrubbed together [11], [12], [13]. Fig. 8 illustrates the functional principle of weldi. . Laser beam welding uses the absorption of electromagnetic waves to heat up the joint partners. The laser beam can be provided by various laser sources [25]. In this study, the laser source. [pdf]
Fusion welding, specifically using electron beams or lasers, is the best method for welding battery components. Both electron beam and laser welding offer high power densities, pinpoint accuracy, and are well-suited for automated welding processes and small, miniature weld applications.
Different welding processes are used depending on the design and requirements of each battery pack or module. Joints are also made to join the internal anode and cathode foils of battery cells, with ultrasonic welding (UW) being the preferred method for pouch cells.
This welding process is used primarily for welding two or more metal sheets, in case of battery it is generally a nickel strip and positive terminal/negative terminal of the battery together by applying pressure and heat from an electric current to the weld area. Advantages: Low initial costs.
Brass (CuZn37) test samples are used for the quantitative comparison of the welding techniques, as this metal can be processed by all three welding techniques. At the end of the presented work, the suitability of resistance spot, ultrasonic and laser beam welding for connecting battery cells is evaluated.
Battery applications often involve welding dissimilar metals, such as copper to nickel, which can be problematic in welding. Commonly used materials in battery construction include copper, aluminum, and nickel.
The findings are applicable to all kinds of battery cell casings. Additionally, the three welding techniques are compared quantitatively in terms of ultimate tensile strength, heat input into a battery cell caused by the welding process, and electrical contact resistance.
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