Abstract: A classification model which classifies contents is provided. Learning contents and contents are included. The learning contents are provided with a first feature and a learning label, and the contents are provided with a second feature. The content classification method includes a step of generating a plurality of first classification models by machine learning using the plurality of learning contents, a step of generating a second classification model with the use of the plurality of first classification models, and a step of providing judgment data for the plurality of contents with the use of the second classification model and performing display on a GUI. The judgment data includes a classification label or a score. The GUI designates a particular numerical range of the score and displays a corresponding content in a list form. Note that features provided for the contents are management parameters (metadata).

Abstract: An object is to suppress electrochemical decomposition of an electrolyte solution and the like at a negative electrode in a lithium ion battery or a lithium ion capacitor; thus, irreversible capacity is reduced, cycle performance is improved, or operating temperature range is extended. A negative electrode for a power storage device including a negative electrode current collector, a negative electrode active material layer which is over the negative electrode current collector and includes a plurality of particles of a negative electrode active material, and a film covering pan of the negative electrode active material. The film has an insulating property and lithium ion conductivity.

Abstract: A novel content classification method is provided. A content classification method using machine learning for a learning model and a classifier fabrication method are provided. In Step 1, a data set containing a plurality of contents is acquired. Learning labels are attached to m contents, and the learning labels are not attached to the remaining contents. In Step 2, a first learning model is created by machine learning using the m contents. In Step 3, judgment labels are attached to the plurality of contents using the first learning model and are displayed on a GUI. In Step 4, new learning labels are attached to k contents in the plurality of contents. In Step 5, a second learning model is created by the machine learning using the k contents. In Step 6, judgment labels are attached to the plurality of contents using the second learning model and are displayed on the GUI.

Abstract: A lithium ion secondary battery includes a positive electrode including a positive electrode active material layer containing lithium iron phosphate, a negative electrode including a negative electrode active material layer containing graphite, and an electrolyte including a lithium salt and a solvent including ethylene carbonate and diethyl carbonate between the positive electrode and the negative electrode. When the battery temperature of the lithium ion secondary battery or the temperature of an environment in which the lithium ion secondary battery is used is T and given temperatures are T1 and T2 (T1<T2), in the case where T<T1, constant current charge is performed until voltage reaches a given value and then constant voltage charge is performed; in the case where T1?T<T2, only constant current charge is performed; and in the case where T2?T, charge is not performed.

Abstract: A power storage device having flexibility is provided. A power storage device of which the capacity is not likely to deteriorate even when being curved is provided. A power storage device includes a first electrode, a second electrode, and an electrolytic solution. The first electrode and the second electrode overlap with each other. The first electrode includes a first current collector and a first active material layer. The first current collector has a first surface and a second surface. The first active material layer is provided on the first surface. The first current collector has a first bent portion with the second surface inside. The second surface includes a first region and a second region. The first region overlaps with the second region. The first region is connected to the second region at a portion different from the first bent portion.

Abstract: Deterioration of a power storage device is reduced. Switches that control the connections of a plurality of power storage devices separately are provided. The switches are controlled with a plurality of control signals, so as to switch between charge and discharge of each of the power storage devices or between serial connection and parallel connection of the plurality of power storage devices. Further, a semiconductor circuit having a function of carrying out arithmetic is provided for the power storage devices, so that a control system of the power storage devices or a power storage system is constructed.

Abstract: To provide a lithium-ion storage battery or electronic device that is flexible and highly safe. One embodiment of the present invention is a flexible storage battery including a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, an exterior body that surrounds the positive electrode, the negative electrode, and the separator, and a wiring provided along the exterior body. At least part of the wiring is more easily breakable by deformation than the exterior body. The wiring is more vulnerable to deformation than the exterior body and thus damaged earlier than the exterior body. Damage to the wiring is detected and an alert is sent to a user; thus, the use of the storage battery can be stopped before the exterior body is damaged.

Abstract: An object is to suppress electrochemical decomposition of an electrolyte solution and the like at a negative electrode in a lithium ion battery or a lithium ion capacitor: thus, irreversible capacity is reduced, cycle performance is improved, or operating temperature range is extended. A negative electrode for a power storage device including a negative electrode current collector, a negative electrode active material layer which is over the negative electrode current collector and includes a plurality of particles of a negative electrode active material, and a film covering part of the negative electrode active material. The film has an insulating property and lithium ion conductivity.

Abstract: Disclosed is a power storage unit which can safely operate over a wide temperature range. The power storage unit includes: a power storage device; a heater for heating the power storage device; a temperature sensor for sensing the temperature of the power storage device; and a control circuit configured to inhibit charge of the power storage device when its temperature is lower than a first temperature or higher than a second temperature. The first temperature is exemplified by a temperature which allows the formation of a dendrite over a negative electrode of the power storage device, whereas the second temperature is exemplified by a temperature which causes decomposition of a passivating film formed over a surface of a negative electrode active material.

Abstract: A decrease in the capacity of a power storage device is inhibited by adjusting or reducing imbalance in the amount of inserted and extracted carrier ions between positive and negative electrodes, which is caused by decomposition of an electrolyte solution of the negative electrode. Further, the capacity of the power storage device can be restored. Furthermore, impurities in the electrolyte solution can be decomposed with the use of the third electrode. A power storage device including positive and negative electrodes, an electrolyte, and a third electrode is provided. The third electrode has an adequate electrostatic capacitance. The third electrode can include a material with a large surface area. In addition, a method for charging the power storage device including the steps of performing charging by applying a current between the positive and negative electrodes, and performing additional applying a current between the third electrode and the negative electrode is provided.

Abstract: Disclosed is a power storage unit which can safely operate over a wide temperature range. The power storage unit includes: a power storage device; a heater for heating the power storage device; a temperature sensor for sensing the temperature of the power storage device; and a control circuit configured to inhibit charge of the power storage device when its temperature is lower than a first temperature or higher than a second temperature. The first temperature is exemplified by a temperature which allows the formation of a dendrite over a negative electrode of the power storage device, whereas the second temperature is exemplified by a temperature which causes decomposition of a passivating film formed over a surface of a negative electrode active material.

Abstract: A decrease in the capacity of a power storage device is inhibited by adjusting or reducing imbalance in the amount of inserted and extracted carrier ions between positive and negative electrodes, which is caused by decomposition of an electrolyte solution of the negative electrode. Further, the capacity of the power storage device can be restored. Furthermore, impurities in the electrolyte solution can be decomposed with the use of the third electrode. A power storage device including positive and negative electrodes, an electrolyte, and a third electrode is provided. The third electrode has an adequate electrostatic capacitance. The third electrode can include a material with a large surface area. In addition, a method for charging the power storage device including the steps of performing charging by applying a current between the positive and negative electrodes, and performing additional applying a current between the third electrode and the negative electrode is provided.

Abstract: In the case where a secondary battery is repetitively curved, portions which tend to cause deterioration such as crack or breakage are, for example, a positive electrode tab and a negative electrode tab. This is because these portions are narrow projected portions, and tend to have low mechanical strength against repetitive curving in some cases. In view of the above, the positive electrode tab and the negative electrode tab are provided in portions relatively less affected by curving. More specifically, secondary battery includes a positive electrode, a positive electrode lead electrically connected to the positive electrode, a negative electrode, a negative electrode lead electrically connected to the negative electrode, a separator, and an exterior body wrapping the positive electrode, the negative electrode, and the separator. The positive electrode, the separator, the negative electrode, and the exterior body can be curved in a first direction.

Abstract: A highly accurate document search, particularly a search for a document relating to intellectual property, is achieved with an easy input method. A document search system includes a processing portion. The processing portion has a function of extracting a keyword included in text data, a function of extracting a related term of the keyword from words included in a plurality of pieces of first reference text analysis data, a function of giving a weight to each of the keyword and the related term, a function of giving a score to each of a plurality of pieces of second reference text analysis data on the basis of the weight, a function of ranking the plurality of pieces of second reference text analysis data on the basis of the score to generate ranking data, and a function of outputting the ranking data.

Abstract: A semiconductor device in which a circuit and a power storage element are efficiently placed is provided. The semiconductor device includes a first transistor, a second transistor, and an electric double-layer capacitor. The first transistor, the second transistor, and the electric double-layer capacitor are provided over one substrate. A band gap of a semiconductor constituting a channel region of the second transistor is wider than a band gap of a semiconductor constituting a channel region of the first transistor. The electric double-layer capacitor includes a solid electrolyte.

Abstract: Deterioration of a power storage device is reduced. Switches that control the connections of a plurality of power storage devices separately are provided. The switches are controlled with a plurality of control signals, so as to switch between charge and discharge of each of the power storage devices or between serial connection and parallel connection of the plurality of power storage devices. Further, a semiconductor circuit having a function of carrying out arithmetic is provided for the power storage devices, so that a control system of the power storage devices or a power storage system is constructed.

Abstract: To provide a lithium-ion storage battery or electronic device that is flexible and highly safe. One embodiment of the present invention is a flexible storage battery including a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, an exterior body that surrounds the positive electrode, the negative electrode, and the separator, and a wiring provided along the exterior body. At least part of the wiring is more easily breakable by deformation than the exterior body. The wiring is more vulnerable to deformation than the exterior body and thus damaged earlier than the exterior body. Damage to the wiring is detected and an alert is sent to a user; thus, the use of the storage battery can be stopped before the exterior body is damaged.

Abstract: A highly accurate document search, particularly a search for a document relating to intellectual property, is achieved with an easy input method. A document search system includes a processing portion. The processing portion has a function of extracting a keyword included in text data, a function of extracting a related term of the keyword from words included in a plurality of pieces of first reference text analysis data, a function of giving a weight to each of the keyword and the related term, a function of giving a score to each of a plurality of pieces of second reference text analysis data on the basis of the weight, a function of ranking the plurality of pieces of second reference text analysis data on the basis of the score to generate ranking data, and a function of outputting the ranking data.

Abstract: A semiconductor device in which a circuit and a battery are efficiently stored is provided. In the semiconductor device, a first transistor, a second transistor, and a secondary battery are provided over one substrate. A channel region of the second transistor includes an oxide semiconductor. The secondary battery includes a solid electrolyte, and can be fabricated by a semiconductor manufacturing process. The substrate may be a semiconductor substrate or a flexible substrate. The secondary battery has a function of being wirelessly charged.

Abstract: A semiconductor device in which a circuit and a power storage element are efficiently placed is provided. The semiconductor device includes a first transistor, a second transistor, and an electric double-layer capacitor. The first transistor, the second transistor, and the electric double-layer capacitor are provided over one substrate. A band gap of a semiconductor constituting a channel region of the second transistor is wider than a band gap of a semiconductor constituting a channel region of the first transistor. The electric double-layer capacitor includes a solid electrolyte.