## 3 Results
### Technology-Function Matrix  
Figure 4 illustrates the technology-function matrix, where X-axis is the function and Y-axis is the technology categories. A bubble graph is a great tool used to visualize the analysis results. The size of the bubble corresponds to patent counts: the larger the bubble, the higher the patent counts. By using the technology-function matrix analysis, the large bubble can be easily and quickly discovered. Moreover, the technology and function paid attention more by patent assignees can be explored. Furthermore, some large bubble also presents the percentage pie chart of patent assignees who lead in innovating technology. Therefore, the technology-function matrix is a useful tool that visualizes the developing trends. Figure 4 shows that the largest bubble locates at AM (electrolyte solutions or electrolyte materials) and AJ05 (cycle life or cycle characteristics). It means that six patent assignees focused more on developing electrolyte materials to improve the cycle characteristics of LIBs. It also indicates that electrolyte composition was a significant impact on cycle life performance. Another much bigger bubble was at HJ (specific numerical limitation, size or scope) and AJ05. It represents that six patent assignees also considered the component ratio in the electrolyte. These patent assignees are also considered in developing battery elements (EJ and DJ), ex: anode, cathode, or separator materials to enhance the performance of cycle characteristics. Charging and discharging characteristics (AJ02),  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Patent** & \multicolumn{3}{c}{**Electrolyte Composition**} \\ \cline{2-4}
**Assignee/** & \multicolumn{1}{c}{**Lithium Salts**} & **Organic Solvents** & **Additives** \\ \hline  & (1) Inorganic lithium salts: LiPF\({}_{6}\), LiBF\({}_{4}\), LiClO\({}_{4}\). & (1) Ethylene carbonate, propylene carbonate. & (1) Overcharge preventing agent, e.g., lithium cyclic & (2) A symmetric linear biphenyl, an alkyl biphenyl, terphenyl, alkylbiphenyl, terphenyl, alkylbiphenyl, terphenyl, a partially hydrogenated product of terphenyl, cyclohexylbenzene. \\  & (2) Lithium cyclic disulfonylimide, e.g., lithium cyclic 1,2-ethanedisulfonylimide, lithium cyclic 1,3-propanediusulfonylimide, lithium cyclic 1,2-perfluoroethanedisulfonylimide, & carbonate, diethyl carbonate, diethyl carbonate, diethyl carbonate, diethyl carbonate, diethyl carbonate, diethyl carbonate, \\ Mitsubishi & lithium cyclic & (3) Organic lithium salts: LiPF\({}_{6}\), LiBF\({}_{4}\)(C\({}_{2}\)F\({}_{5}\)SO\({}_{2}\))\({}_{2}\), LiN(CF\({}_{3}\)SO\({}_{2}\))\({}_{3}\), LiF\({}_{4}\)(C\({}_{2}\)F\({}_{5}\)SO\({}_{2}\))\({}_{2}\), LiF\({}_{4}\)  
capacitive characteristics (AJJ03), and safety security or explosion proofing (AJ12) are also important issues concerned by them. The percentage numbers in the AM-AJ05 bubbles also show that Japanese assignees have more than 70% of the patents and Mitsubishi Chem. and Panasonic owned more issued patent counts. Korean firms seem to emphasize more on safety issues (AJ12) while developing electrolyte material. Table 3 shows the representative patents of them with the highest forward-citation counts in the USPTO database. It is interesting to note that Mitsubishi Chem., Panasonic, LG Chem., and Samsung SDI all used the similarly mixed lithium salts and mixed organic solvents systems. The most different part in the electrolyte is the selection of additives. Mitsubishi Chem. (US7083878B2) used overcharge preventing agents, such as cyclohexylbenzene, t-butylbenzene, and t-amylbenzene, to improve cycle characteristics after storage at high temperature. Panasonic (US6958198B2) mixes the fluorine-containing compound, e.g., fluoroalkyl(C2-C20)carboxylic acids, with the carbonate and sulfur compound to provide LIBs in excellent cycle life. Samsung SDI (US7205073B2) combines the anisole compound, ex: 3-fluoroanisole, sulfone-based compound, and poly(ester)(metha)acrylate, to improve the safety of LIBs. LG Chem.