EVALUATION OF ELECTRIC CAR RESEARCH TRENDS THROUGH BIBLIOMETRIC ANALYSIS: A Literature Review

adoption of electric

Research on electric vehicles in the current academic literature primarily focuses on factors influencing electric vehicle adoption behavior [33,34] and Infrastructure of service facilities for battery charging [28,33].Government policies or incentives to aid electric vehicle adoption [ [34][35][36] and operation planning [37,38].
Electric vehicles (E.V.s) have three essential components that support vehicle operation: batteries as an energy source for electric cars, electric motors as drives that produce mechanical energy, and propulsion systems that transfer mechanical energy to the vehicle's wheels [39].
1. What is the annual publication in the field of Electric vehicle product development?2. What are citation trends and the number of their uses in the SCOPUS database?3. How are product development-related publications distributed?4. What are the most influential countries, journals, and institutes? 5. Which research groups, countries, and organizations are most productive by citation and bibliography?6.What topics arise related to the development of electric vehicle products?7. How are existing publications spread?8. What keywords are related to each other?

RESEARCH METHOD Data sources
Scopus is used in many countries as a trusted journal for academic advancement or an evaluation for funding by institutions [42] [40].As a growing bibliographic database, Scopus is increasingly used in academic research and evaluation practice [41].Data was taken on January 17, 2023, from the SCOPUS collection using the keywords "electric vehicle" OR "electric vehicles" OR "E.V." AND "product development."As many as 300 documents related to the product development of electric vehicles were obtained.The first document was published from 1986 to 2023.

Bibliometric Methods
Vosviewer was used in this study for dataset development [42].Vosviewer is free software for building and visualizing bibliometric networks [45].These [43] can consist of journals, research, or personal publications built on keywords, citations, abstracts, bibliographies, shared citations, or co-author relationships [46] [44].

Inclusion and Exclusion Criteria
The search starts with keywords related to electric vehicles ("electric vehicle" OR "electric vehicles" OR "E.V.") and then about product development on the SCOPUS search engine.A total of 300 documents emerged from 1986 to 2023.The publication consists of 6 languages, namely English (285), Chinese (7), German (7), Italian (1 ), Japanese (1) and Turkish (1).In this study, we agreed only in English.The remaining 285 documents in English consist of a conference paper (130), an Article (112), a conference review (29), a review (7), a Book chapter (4), a short survey (2), and a note (1).It was found that several terms overlapped and were issued manually [47][45], Such as automobile cooling systems, automobile manufacture, and automobiles becoming one term automobiles.Commerce and commercial vehicles have become one term: commercial vehicles.Electric Vehicles and Electrical Vehicles become one term: Electric Vehicle.Hybrid Electric Vehicles, Hybrid Electric Vehicles, and Hybrid Vehicles have become one term, hybrid electric vehicle.Lithium, lithium batteries, and lithium-ion batteries become one term lithium batteries.Powertrain and powertrains became one powertrain term.The set of documents by type can be seen in Figure Figure 1.Types of final documents.

Data analysis
The final data is exported from SCOPUS in CSV format and analyzed in detail.The characteristics of bibliometric mapping to be carried out are Co-authorship maps, consisting of authors, organizations, and countries; citation maps, consisting of publications, journals, and authors (first author); bibliographic coupling maps, consisting of magazines, journals, authors, organizations, and countries; Subject mapping/keywords (co-occurrence maps), consisting of keywords and terms from the title and abstract.

Global Publications and Excerpt Output
Annual publications can generally be seen in Figure 2. Annual publications.Publications in the field of electric vehicle product development have increased.The increase in the number of publications is divided into three time periods, namely 1986 to 2011 (old paper), 2012 to 2018 (recent paper), and 2018 to 2022 (current paper).In 1986, there was one article with the theme of product development.In 2005, there was a sudden high increase in publications.From 2012 to 2018, the number of publications was relatively stable, and there was an increase in 2015.From 2019 to 2020, there was an increase in publications compared to the previous period.There was a significant increase in citations in 1999, as many as 104 citations, considering that research on electric car design increased that year.The number of citations until December 2022 is 2576 citations.

Figure 3. The number of citations
The number of scientific works is directly related to the reader's liking.Generally, readers prefer to read the latest articles; however, frequently cited articles use more old-year publications, whereas the latest articles also include quotes from old articles.This causes the latest article to have fewer citations than the old one because new articles take time to be quoted.This is following Wang's research on Usage patterns of scholarly articles on Web of Science: a study on Web of Science usage count.Scientometrics [46].The following article is the most summarized quote in Table 1.Top 10 Citation.The table contains details, quotes, and the number of quotes.

Publication Distribution
In total, 29 countries contribute to the development of electric vehicle products.As of this writing, it is sorted by the most dominant countries in research contribution.The most dominant countries in this study can be seen in Figure 4.The number of publications sorted from the most are United States (56), Germany (60), China (24), India (24), Japan (14), United Kingdom ( 14), Brazil, France, Italy and the Netherlands 7 documents each, and others (27).Based on these data, it was found that the United States became the dominant country, followed by Germany.The most dominant journals are summarized in F. It can be seen that the National Natural Science Foundation of China is the most popular, with seven articles published, followed by the Bundesministerium für Bildung und Forschung.

Subject Categories Research Productivity
Based on the subject categories contained in the Vos Viewer web science, from the data output of research publications related to the development of electric vehicle products spread across 19 subject categories for twenty years.There are 11 subject categories shown in Figure 6.The three most prominent fields are engineering, energy, and computer science.

CONCLUSION AND SUGGESTION
This study summarizes the research domain regarding the development of electric vehicle products from one view.This paper shows that research in this area has remained attractive for the last 10 years and will remain an exciting topic in the coming years.Some of the key findings in this study include the most dominant country in scientific publications on the development of electric vehicle products, United States, with 56 publications, followed by Germany, with 50 publications.Meanwhile, the National Natural Science Foundation of China is the institution that has the most publications, with seven publications, and the second position is the Bundesministerium für Bildung und Forschung, with six publications.The keywords that appear most often product development, electric vehicle, and product design.
Please note that this study has limitations.Among them, this analysis is based on data provided only by SCOPUS.Of course, this is one of the most trusted sources of information.However, the results may differ when adding sources of information other than SCOPUS.This study does not cover co-authorship from the author, organization, or state.

Figure 1 .
Figure 1.Types of final documents

Figure 4 .
Figure 4. Dominant Countries in Research A total of 267 organizations or affiliates contributed to the study.The most dominant institutions in this study can be seen inTable The Technical University of Munich is the most dominant institution in this research, followed by Karlsruher Institut für Technologie.

Figure 5 .
Figure 5. Subject categories by field of research

Table 2 .
Table The Technical University of Munich is the most dominant institution in this research, followed by Karlsruher Institut für Technologie.shows the top publishing institutions in the research domain

(yellow): 11 items: simulation and performance of electric vehicle product development
6. Analysis Co-occurrence of research themes from abstracts Article, carbon dioxide, curricula, electric machine control, engines, internal combustion engines, performance, powertrain, simulation, students, vehicles 5.

Cluster 5 (Purple): 8 Items: new product development electric vehicle product development
Automotive product development, battery pack, decision making, electric drives, electric traction, hybrid electric vehicle, new product development, traction motors 6.

Cluster 6 (light blue): 4 items: energy electric vehicle product development
Traction motors, energy storage, patents and inventions, secondary batteries 7.